Refrigeration



Dec. 1942- H. M. ULLSTRAND v 2,306,199

REFRIGERATION Filed June 4, 1938 M WWW M q i' TTORNEY.

7 proved circulation of of the above-mentioned type fully understood upon description and accompanying drawing forming 40 Patented Dec. 1942 UNITED STATES 2,306,199 REFRIGERATION Hugo M. Ullstrand, Stockholm, Inc., New York, N.

to Serve], of Delaware Sweden, assignor Y., a corporation Application June 4, 1938, Serial No.'211,749

8 Claims. My invention relates to refrigeration; and more particularly to refrigeration systems of the kind employing an inert gas or pressure equalizing 4 agent.

In refrigeration systems ofthis kind liquid refrigerant fluid flows from a condenser and evapcrates and diffuses into an inert gas in an evaporator or cooling element to produce a refrigerating efiect. The resulting rich gas mixture of refrigerant and inert gas flows .in a gas circuit from the cooling element to an absorber in which refrigerant gas is absorbed into absorbent. Inert gas weak in refrigerant flows in the gas circuit from the absorber back to the cooling element and preferably in heat exchange relation with rich gas flowing to the absorber.

It is an object of my invention to provide imfluid in systems of the above-mentioned typehaving a plurality of cooling elements. This is accomplished by supplying liquid refrigerant fluid from a first part of a condenser to one-\of a plurality of cooling elements connected in parallel in a gas circuit, and supplying liquid refrigerant fluid consecutively to one or more other cooling elements from subsequent portions of the condenser.

It is another object of the invention to provide an improvement for controlling the circulation of inert gas or pressure equalizing agent in systems having a plurality of cooling elements. This is accomplished by automatically effecting a reduction in the flow of inert gas in the gas circuit when the load is reduced, thereby improving the eiflciency of the refrigeration system. I

The invention, together with the above and other objects and advantages thereof, will be more reference to the followinga part of this specification, and in which the single figure illustrates more or less diagrammatically a refrigeration system embodying the invention. In the drawing the invention is embodied in an' absorption refrigeration system of a type containing a pressure equalizing agent. Such a system includes a generator I0, condenser I I, a cooling unit I2, and an absorber I4 which are interconnected in a manner well-known in the art and which will briefly be described hereinafter. The system contains a solution (if refrigerant in absorption liquid, such as ammonia in water, for example, and also an auxiliary agent or inert gas, such as hydrogen. The generator IIi is heated in any suitable manner, as by a gas burner I 5, for example, wherebv refrigerant vapor is expelled from solution in generator III. The refrigerant vapor flows upward through a stand-pipe I6 anda conduit I1 into the condenser II in which it is liquefied. Liquid refrigerant flows from condenser II into cooling unit I2 through conduits I8 and I9, as will be described hereinafter.

Refrigerant fluid in cooling unit I 2 evaporates and diffuses into inert gas which enters from the upper end of an outer conduit 20 of gas heat exchanger 2I.- Due to evaporation of refrigerant fluid into inert gas, a refrigerating effect is produced with consequent absorption of heat from the surroundings. The rich gas mixture of refrigerant vapor and inert gas formed in cooling unit I2 flows from the upper parts thereof through the inner conduit '22 of gas heat exchanger 2I and conduit 23 into the lower part of absorber I4.

In absorber I4 the rich gas mixture flows counter-current to downwardly flowing weak absorption liquid which enters through a conduit 24. The absorption liquid absorbs. refrigerant vapor from the inert gas, and'inert gas weak in refrigerant flows from absorber I4 through aconduit 25 and outer conduit 20 of gas heat exchanger 2I into the lower parts of cooling unit I 2. The circulation of gas inthe gas circuit just described is due to the difierence in specific weight of the columns of rich and weak gas in the inner and outer conduits 22 and gas heat exchanger 2|. Since the rich gas is I heavier than the weakgas, a force is produced or developed for causing flow of rich gas toward absorber II and flow of weak gas toward cooling unit I2.

Absorption liquid enriched in refrigerant flows from the lower part of absorber II through a conduit 26, outer passage of a'liquid heat exn r I. and conduit-.28 into generator III. quid is raised in the generator by a. thermosiphon tube 29 and flows back to the generator through stand-pipe I 6. The refrigerant vapor xpelled out of solution in generator III, together with refrigerant vapor entering through thermosiphon tube 29, flows upwardly through standpipe I6 and conduit II into condenser I I, as explained above.

The absorption liquid from which refrigerant has been expelled flows from generator III through conduit 20, inner v 21, and conduit 24 to the upper part of absorber This circulation of absorption liquid results from the raising of liquid by thermosiphon tube 29. Heat liberatedwith absorption of refrigerant vapor in absorber I4 is transferred to a suitable cooling 20, respectively, of the passage of liquid heat exchanger medium which'circulates through a coil cooling unit l2 decreases,

, reduces the heat input 3| arranged in thermal exchange relation with the absorber.

The lower end of condenser H is connected by conduit 32, vessel 33, and conduit 34 to the gas circuit, so that any inert gas which may pass through the condenser can flow into the gas circuit. Refrigerant vapor not liquefied inthe condenser fiows through conduit 32 to displace inert gas in vessel 33 and force such gas through conduit' 34 into the gas circuit. By forcing gas into the gas circuit in this manner, the total pressure in the system is raised whereby an adequate condensing pressure is obtained to insure condensation of refrigerant vapor in condenser The refrigeration system just descr'bed may be controlled by a thermal bulb 35 which is affected by a temperature condition of cooling unit l2. As shown, the thermal bulb 35 is arranged in thermal exchange relation with a bottom part of cooling unit I! and connected by a conduit 38 to a control device 31 which is connected in a fuel supply conduit 38 of burner l5. The thermal bulb, 35 and conduit 35 may form part of an expansible fluid thermostat which is charged with a suitable volatile fluid and responds to changes of temperature of cooling trol device 31, in a manner well-known in the art.

When the temperature of cooling unit I! increases due, for instance, to increase in heat load caused by placing of warm material in the refrigerator, or rise in room air temperature, the thermal bulb 35 becomes efifective to operate control device 31 to increase the supply of fuel to burner l5. Thisincreases the heat input and hence the rate at which refrigerant vapor is expelled from solution in generator I, thereby increasing the amount of refrigerant vapor which condenses in condenser II and flows into cooling unit l2. Conversely, when the temperature of the thermal bulb 35 becomes effective to operate control device 31 to sulting from the difference 't I! to operate condecrease the supply of fuel to burner l5. This and hence rate at which refrigerant vapor is expelled from solution in generator ||i, thereby decreasing the amount of refrigerant vapor which condenses in condenser and flows into cooling unit I2. i

In accordance withthe invention the cooling unit I! includes a plurality of cooling elements 33 and 40 which are connected in parallel in the gas circuit and consecutively supplied with liquid refrigerant from subsequent sections of condenser II. The parallel connection of cooling elements 39 and 43 in the gas circuit will be readily apparent in the drawing wherein the lower ends of the cooling elements are connected to the upper end of outer conduit 20 of gas heat exchanger 2|.

The upper ends of cooling elements 33 and 43 are connected by conduits tively, to a header 43 at the upperend of inner conduit 22 of gas heat exchanger 2|. The lower end of conduit 34 is shown connected to the gas circuit at the upper end of conduit 4|. It is to be understood, however, that conduit 34 may be connected to the gas circuit at any other convenient point.

Refrigerant vapor from generator ll flows upward through conduit ll into upper condenser section Ila. Refrigerant liquefied in condenser section a flows into gas separatin chamber 44 and thence through conduit l3 into the upper part of cooling element 33. Refrigerant not liquefied in .upper condenser section ||a flows from the upper part of chamber 44 into lower 4| and 42, respecthermostat is shown in lower condenser section III) flows therefrom into a gas separating chamber 45 and thence through conduit l9 into the upper part of cooling element 40.-

The thermal bulb 35 of the expansible fluid thermal contact with the bottom part of cooling element 33 for controlling the rate at which fuel is supplied to burner l5 and hence the heat input to generator In As pointed out above, the circulation of gas in the gas circuit is effected by force produced or developed within the system, such force rethe columns of rich and weak gas. in the rate of gas flow inherently takes place with a decrease in load, due to the fact that less liquid refrigerant evaporates in the cooling elements. The efliciency of the refrigeration system is improved considerably, however, when a further reduction in the rate of gas flow is effected with decrease in load, so that the rate of gas flow is better correlated to the load and the heat input to the generator l0.

By effecting a further reduction in the rate of gas flow, less weak gas flows upwardly from absorber M. This weak gas must be cooled when it enters cooling element 39, for example. By reducing the circulation of weak gas so that it is better correlated to the load or capacity, less cooling of such gas need be effected when cooling element 33 is operating at low load and reduced heat input. I

In accordance with the invention, a reduction in the rate of gas flow is effected under certain operating conditions by connecting cooling elements 33 and 43 in parallel in the gas circuit .and consecutively supplying liquid refrigerant case normal circulation of inert gas is effected through cooling elements 33 and 40 with weak gas entering the lower parts and with rich gas leaving the upper parts and flowing together in header 43.

Under certain operating conditions all of the refrigerant vapor may be condensing in upper condenser section Ila and no refrigerant vapor may be condensing in lower condenser section III). This will occur, for example, when the load is low and the heat input to generator In is reduced.

Vifith no liquid being supplied to cooling element 4! the weak gas circulating therethrough will not be enriched with refrigerant vapor. In such case weak gas leaves the upper part of cooling element 43 and mixes in header 43 with rich gas flowing through conduit 4| from the upper part of cooling element 33. Due to such mixing of weak and rich gas, the specific weight of the condenser section llb. Refrigerant liquefied in 76 column of rich gas in inner conduit 22 of gas heat exchanger 2| is reduced. This reduces the difference in specific weight between the columns of rich and weak gas, thereby lowering the force that is produced or developed within the system for causing flow of gas. This reduction in the rate of gas flow is eifected automatically and better correlates the rate of gas flow with the load and the heatinput to the generator, thereby improving the efliciency of the refrigeration system.

Since no evaporation of liquid into weak gas takes place in cooling element 43 when refrigerant in specific weight of h A reduction place at a faster rate thanthe rate at which vapor is not condensing in lower condenser section lib, useless and unnecessary flow of weak gas through cooling element 40 may be avoided by providing a suitable by-pass. Such by-pass may include a vessel 46 at the lower end of cooling element 40 into which liquid refrigerant can liquid flows into the vessel. Whenever the load conditions and heat input change so that the condensation of refrigerant vapor in lower condenser section llb is reduced, therefore, the liquid level in vessel 46 will immediately begin to fall to efiect a reduction in the rate of gas circulation. As soon as the lower end of by-pass conduit 5| is open due to fall of liquid level in vessel 46, the relative rate of gas flow in cooling elements 39 andv 40 will be changed. Further, in addition to reducing the flow of gas in the entire gas'circuit due to by-passing of gas through conduit 5|, the flow of gas in cooling element 40 exchanger 2|, whereby unevaporated liquid may be drained from the bottom of cooling element 39.

A conduit 5| is connected to header 43 and extends downward into vessel 46 to provide a bypass or vent in the gas circuit. When the amount of liquid accumulated in vessel 46 is such that the lower end of conduit 5| is sealed by liquid,

the by-pass conduit 5| is closed and all of the gas'entering vessel 46 from conduit 29 flows through cooling element 40. When the liquid level in vessel 46 falls so that the lower end of conduit 5| is open, gas entering vessel'46 from conduit will flow through conduit 5| and thereby reduce the flow of gas through cooling element 40.

With the load and heat input such that refrigerant vapor condenses in both condenser sections Na and Nb, liquid is supplied to cooling element 40 as well as cooling element 39 and liquid may accumulate in vessel 49 to close bypass conduit 5|. In such case normal circulation of inert gas is effected through cooling elements 39 and 40 with weak gas entering the lower parts and with rich gas leaving the upper parts and flowing together in header 43. I

With no liquid being supplied to cooling element 40, as at low load and with reduced heat input to generator II), the liquid level in vessel 46 falls due to evaporation of liquid into weak gas. When the liquid level falls sufliciently in vessel 46 so that the by-pass conduit 5| opens, gas entering vessel 46 from conduit 20 will flow through conduit 5| into header 43. This reduces the flow of gas in cooling element 40 and the diverted gas flowing through conduit 5| mixes with rich gas flowing into header 43 from the upper part of 'cooling element 39. In this way the specific weight of the column of rich gas is reduced, thereby reducing the force developed or produced in the system for causing flow of gas inthe gas circuit.

When by-pass conduit 5| is open and no liquid is flowing from lower condenser section lb into cooling element 49, the'cooling element 39 is' operative to take care of the low load existing under such conditions. With increase in load,

the thermal bulb of the expansible fluidthermostat responds to operate control device 31 to increase the heat input to generator Hi. When refrigerant vapor is condensed in lower condenser section II b due to such increase in load and at higher heat input, by-pass conduit 5| closes due load, therefore, cooling element becomes operative to take care of part of the load.

will be reduced. v

While a single embodiment of the invention has been shown and described, such variations and modifications are contemplated as fall within the true spirit and scope of the invention, as pointed out in the following claims. Whatisclaimed is: 1. In a method of refrigeration-with the aid I of a system having a circuit for inert gas ineluding a plurality of places of evaporation and in which circulation of inert gasis .due to the difference in specific weight of columns of gaseous fluid, the improvement which consists in flowing liquid refrigerant to said places of evaporation, flowing inert gas through said places of evaporation in parallel, and decreasing the difference'in specific weight of said columns of gaseous fluid to reduce the rate of gas circulation by reducing the flow of liquid refrigerant to one of said places of evaporation relative to theflow of liquid refrigerant to another of said places of evaporation. I

2. In a method of refrigeration with the aid of a system having a circuit including a plurality of evaporators in parallel for circulation of inert gas, that improvement which consists in accumulating liquid refrigerant at a place of accumulation, and reducing the circulation of inert gas through one of said evaporators relative to the circulation of inert gas through another of said evaporators with decrease in the amount of liquid refrigerant at said place of accumulation.

3. In a method of refrigeration with the aid of a system having acircuit for inert 'gas' including a plurality of evaporators and in which circulation of inert gas is due to the difference in specific weight of columns of gaseous fluid rich and weak, respectively, in refrigerant vapor, that improvement which consists in circulating inert to rise of liquid in vessel 46. With increase 'in By connecting cooling elements 39 and 4 0 in parallel in the gas circuit andproviding bv-p'ass conduit 5|, the liquid level in vessel 46 will fall gas through said evaporators in parallel, accumulating liquid refrigerant at a place of accumulation, and, with decrease in the amount of liquid regrigerant at saidplace of accumulation, diverting weak gas flowing to one of said evaporators and flowing such diverted gas into the column of gaseous fluid rich in refrigerant vapor.

4. A refrigeration system including a plurality of coolingelements, means to conduct liquid refrigerant to said cooling elements, connections for circulation of inert gas through said cooling elements, means for receiving liquidand holding such liquid in contact with circulating inert gas,

and means responsive to level 'of liquid in said receiving means to vary relative to each other the relative amounts of inert gas circulating respectively through said cooling elements.

5. A refrigeration system including an inert gas circuit having a plurality of cooling elements connected in'p'arallel, a by-pass connection for inert gas around one of said coolingelements,

and means for controllingsaid by-pass connection.

6. A refrigeration system including an inert gas circuit having a plurality of cooling elements connected in parallel and through which circulation of gas is effected by thedifference in specific weight of columns of gaseous fluid rich and weak, respectively, in refrigerant vapor, a bypass connection around one of said cooling elements to permit flow of gas from said column weak in refrigerant; vapor to said column rich in refrigerant vapor, and means for controlling said by-pass connection.

7. A refrigeration system including an inert gas circuit having a plurality of cooling elements, means to conduct liquid refrigerant to said cooling elements an inert gas circuit including said cooling elements and through which gas circulates, circulation of inert gas in said circuit being due to the difference in specific weight of columns of gaseous fluid rich and weak, respectively, in refrigerant vapor formed in said cooling elements, means for receiving liquid refrigerant and holding such liquid in contact with circulating inert gas, a .by-pass connection around one only of said cooling elements to permit flowof gas from said column weak in rea connected in parallel and an absorber, refrigerant fluid liquefying means for supplying refrigerant liquid individually to said cooling elements, and structure in said gas circuit operative to decrease rate of gas circulation in said circuit when supply of refrigerant liquid to one of said cooling elements stops.

HUGO M. UIIS'IRAND. 

